Obviously I wont be able to explain everything but I will try and summarize. Florida operates under the Criminal Punishment Code Scoresheet. Each Primary offense (current offense) is scored as well as any additional offenses. Then they also score your prior record under prior offenses. The primary offense is given a level for instance Grand theft > 300 but less than 5000.00 is a level 2 and scores 10 points as a primary offense. However, DUI causing serious bodily injury is a level 7 and will get you 56 points. There can also be points added for more serious injuries. i.e. severe or moderate. If you score more than 44 points with your primary offense, additional offenses and prior offenses then the judge must sentence you to state prison. There are exceptions like a downward departure. This is where the Judge must state on the record that he is departing from the prison sentence and give legal reasons under the law. On any felony you can get prison time but as previouslsy stated if you score more then 44 points you must be sentenced to prison unless there is a reason to depart from the sentence. I have attached a great link which explains this complicated system. http://www.dc.state.fl.us/pub/sen_cpcm/cpc_manual.pdf
The previous answer by Attorney Finebloom is right on target and the link probably has all the information that is sought by this question. What I wish to add is that regardless of what one scores, the Assistant State Attorney can request and the Judge can sentence an offender up to the statutory maximum regardless of the scoresheet tally. A typical scenario of such is if a defendant gets a felony driving on a suspended license (DWLSR) charge as their primary offense. A felony DLWSR is a third degree felony and a level 1 offense, which merely gives an offender 4 points. However, this offender may have 10 prior felony DWLSRs. Because felony DWLSR is such a low level offense and the prior DWLSR offenses score so little on the scoresheet, this individual may score "non-state prison" (under 44 points). However, the State and the Judge may feel that regardless of the scoresheet, prison is a more appropriate sanction and can accordingly sentence that individual to up to 5 years incarceration in the Department of Corrections.
One other issue that sometimes surfaces is when an individual scores higher than the statutory maximum. For instance, even though one's primary offense is a third degree felony, punishable by up to 5 years incarceration, they may score greater than 60 months. This is generally because that individual has an extremely bad prior record. When this occurs, the court is supposed to sentence the individual according to the higher guidelines sentence.
Another useful thing that a lawyer should always do is carefully review with the client the "prior criminal history" alleged in the scoresheet. Sometimes, offenses are included that are not the client's. Also, if it's an out of state prior, be sure that the "crime" is score as what it is in Florida, not the other state. Sometimes, this can lower the score and save the client from going to prison if the points get below 44.